The reactivity of the trapping reaction of the benzene-bridged boron/phosphorus-based frustrated Lewis pair with difluorocarbene and its group 14 analogs: A theoretical investigation

The trapping reactions of carbene analogs G14F(2) (G14 = group 14 element) by the benzene-bridged B/P-Rea frustrated Lewis pair (FLPs) molecule are studied using density functional theory (B3LYP-D3(BJ)/def2-TZVP). Our theoretical investigations predict that only the CF2 intermediate rather than other heavy carbene analogs can be trapped by the B/P-Rea FLP-type molecule. Energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) analyses indicate that the bonding nature of the G14F(2) catching reactions by the B/P-Rea FLP-type molecule is a donor-acceptor (singlet-singlet) interaction rather than an electron-sharing (triplet-triplet) interaction. Moreover, EDA-NOCV and frontier molecular orbital (FMO) theory findings strongly suggest that the lone pair (LP) (P) -> vacant p-pi-orbital (G14F(2)) interaction rather than the empty sigma-orbital (B) <- sp(2)-sigma-orbital (G14F(2)) interaction plays a predominant role in establishing its bonding condition during the G14F(2) trapping reaction with the B/P-Rea FLP-associated molecule. Our activation strain model findings reveal that the atomic radius of the G14 element of G14F(2) plays a key role in determining the activation barrier of the G14F(2) trapping reactions by the benzene-bridged B/P-Rea FLP. The valence bond state correlation diagram (VBSCD) model developed by Shaik is used to rationalize the calculated results. The VBSCD findings demonstrate that in the present trapping reactions, the singlet triplet splitting of G14F(2) plays a significant role in influencing its reaction barrier and reaction enthalpy. Our theoretical results demonstrate that the relationship between the geometrical parameters of the transition states and the corresponding reaction free energy barriers agrees well with the findings based on the Hammond postulate.